/Engine/Source/Runtime/SandboxFile/Public/IPlatformFileSandboxWrapper.h
Open a file for async reading. This call does not hit the disk or block.
Close the file by delete'ing the handle. A non-null return value does not mean the file exists, since that may not be determined yet.
virtual [IAsyncReadFileHandle](API\Runtime\Core\Async\IAsyncReadFileHandle) * OpenAsyncRead ( const TCHAR * Filename )